Tube covering



7, 1934. H. E. KLEFFEL 1,969,374

TUBE COVERING Filed March 27,' 1951 2 Sheets-She et 2 INVENTOR. W BY Patented Aug. 7, I934 TUBE oOYE I'NG Y Harrison E.Klefiel, New York, N. Y. Application March 27, 1931, seria No. 525, 32 12 Claims. (01. 137-100) This 'invention' relates to improvements in tubes for usein'the furnace chambers of boilers,

oil stills and other apparatus of that sort forthe purpose of breaking up Stratification of and produc'ing turbulence in the 7 stream of burning gases so asto promote combustion. More par-' ticularly, the invention is concerned with prote'cted or covered tubes which are provided with a' covering around their total circumference and throughout such lengths thereof as are to be exposed directly to the furnace temperature, the covering being selected to control the rate of heat'transfer through the .tube walls to the contents of "the tubes and also acting to reflect 5 heat back into thefurnace cavity to further promote combustion. j f

In my co-pending application; Serial No. 439,-

349, filed March 27, 1930, now United States Patent No. 1,884,741, issued October 1932, I have scribed in which covered tubes are disposed in the furnace cavity of a boiler furnace, oil still, etc. in the region where combustion is taking place and serving the purpose above referred to, and-have also described and claimed certain forms of coveredtubes. The tubes disclosed in the present application constitute further modificationsof'and improvements "upon those set forth in theprior application but involve thev same principles of construction and operation. In the prior application, the tubes disclosed are provided with coverings constructed either with a refractory or a metallic outersurface. In both instances, the coverings are firmly anchored to the tube and in effect constitute an integral part thereof. In the first constructiomthe tube is provided with a metallic sleeve shrunk on the tube and having means by which the refractory may be held thereon, such as dovetail connecg tions. In the second construction, the tube is first covered with refractorymaterial Whichis held inplace by an outer sleeve of metal. j Such tube coverings are not tobe confused with refractory tile sleeves, either cylindrical or semi-cylindrical, which have; heretofore ,been used to some extent in boiler installations. A single row of tubes with such sleeves have been em'ployed for'the furnace walls or in some instances tubes with sleeves extending part of their length have been placed in the path of the furnace gases; When such refractory sleeves'are mounted ontubes, arr-intimate contact between the covering and the tube cannot be obtained because the inherent mechanical weakness 0f the -55 refractorypr'events the latter from bcing tightly setforth and'claimed apparatus of the type de clamped in place. The refractory. and tube'expand at different rates and this causes anair gap-between the refractory andtubewhichres duces the -rate of .heattransfersand'frequently results in'thedestruction of the refractorywhen subjectedto furnace: temperatures, or, if therefractory is tightly clamped to the tube, the. difference temperature causesnthe refractoryjto becra'cked. U 3 r Z In my present .tubes, the tube covering is placed inposition under such' conditions as. to produce an intimate contact between th'etube and cover! ing at. all times'and this result is obtained Without; the liability of cracking or spawling there's fractoryzwhen'it is exposed to operating condi-. tions. I

- My form of :tube covering also, has theladditiona1 advantages-in that the metallic sleeve provides added strength-to the-tube against bending and bursting. helps todistributethe-heat more uni formly over. the tubesurface and also provides a protective covering for the tube itself againstthe oxidation and erosive action ofthe' flame. i

For a better understanding of the invention, referencemay be had to the accompanyingv draw-7 ingsinwhichz Q Fig. 1 is a transverse view of tubing; V Fig. 21s a side elevation of the tube illustrated in'Fig; 1, withcertain parts ;;brokenaway,and shown in section; 7. p

Fig.3 is a transverse sectional view of amodified construction? 1 f 1: 3 Fig. 4 is a. transverse section of a special tube in which the tube and a part-of thecovering-are made integral; l 7,1 l Fig. 5Vis a sectional View of a, modified form of the tube shown in Fig. 4; g Fig. 6 is atransverse sectional View of another tube; Fig. '7 is a longitudinal sectional view of construction shown in Fig. 6; I i

r Fig; .8 is a sectional view on theline 8r- 8 of Fig. 9 of a modified'construction in which air spacesareused as an insulator between the .tube

andits outercovering layer; 1 1 Fig. .9, is allongitudinal sectional view of the constructionshownin Fig. 8, thetube being shown in elevation; 1 Fig. -,10 is a fragmentary-sectional view show-'- ingia modification of the construction illustrated inFig.:8 Y 1. Figs. 11 and 12 .are transverse and longitudinal onetype of the new the sectionsfof. a modified form offthe construction Fig. 13 is a transverse section'of a modification of the construction illustrated in Figs. 1 and 3,

Fig. 14 is a view in side elevation with parts shown in section of the construction illustrated in Fig. 13; and

Figures 15 to 19, inclusive, are views corresponding to Figures 8 to 12, inclusive, but illustrating a modified construction.

Referring now to'the. drawings, there isillustratedin Figs. 1 and 2 a conventional tube20 provided with a covering which comprises a metal sleeve 21 in intimate contact with the outer surface of the tube and provided with lengthwise dove tail grooves 22 and projections 23 between,

Mounted on the sleeve are "insulating or refractory segments 24,;these'; segments being anchored in the grooves and separated ,by

the grooves.

expansion material 25 providing longitudinal joints between the sides of adjacent segments x '1 serving to take up expansion inthe sleeves-1:

In constructing the tube, the'metal sleeve is heated andithe. sleeve shrunk in place. The re-tfractory segments are preferably placed in position on the-sleeverwhile the latter is heated .so that when the sleeve cools off and shrinks it grips the tube tightly and also grips .the tongues 28101? the refractory which lie inthe dovetail grooves of the sleeve: Intimate contact of the refractory withthe metal sleeve is thusobta-ined aswell as intimate contact between the metal sleeve and greater rate than the tube and that-part of the sleeve "which is in intimate contact with the tube and kept'rel'atively cool by heat transfer to the contents of the tube. Consequently as there fractory expands due to an increase in temperature,-itis-held more firmly in the dovetail grooves; Instead of employing a complete-refractory covering over themetallic sleeve as illustrated in Figs. 1 and 2, I may use the construction illustrat 1 ed in Fig. '3 in which the'tube 20 is provided with a sleVeZl-having dovetail grooves and projections as before. In the groovesiis placed refracmy or'insulating material '29,:this material-projecting slightly beyond or terminating'fiush'with the surface of the sleeve but-not covering. the tops of the projections thereon. The refractory material may be in suitable lengths or sections, provided at their ends with expansion joints as illustrated in Fig. 2. 1 1 Instead.- of employing a separate metallic sleeve for the purpose of anchoring the refractory, I may produce a special tube illustrated in Fig."- 4. in which the tube and sleeve areformed integral. Sucha tube '30 may bemade by extrusion or drawing and-is provided: with dove tailgrooves 3'1 and integral projections 32 similar to those ordinarily formed on the sleeve. In the'grooves. areplace'd sections-33 of refractory or insulating material which are-flushwith or project outwardly be'yond the face of the tube but do not coverthe'tops of the integral projections thereon. In Fig". 5, there is shown-a modified form-of the constructionillus trated in Fig. 4, in which the tube 30 is provided withgro'ove's and projections with segments1-34 of insulating'or refractory material anchoredin-the grooves and covering the, tops of the; projections.

' stube 20 is provided with an outer metallic sleeve 35 which, if desired, may be made in short lengths 35 and 35 for instance, Fig. '7. Between the metal sleeve and the tube is placed insulating or refractory material 36 by which the rate of heat transfer to the tube-may be regulated and controlled. The sections of the sleeve may, if desired, be provided with inwardly extending flanges 37 andbetween adjacent sections isplaced expan sion material 26,- this expansion material also separating the ends of adjacent portions of, the insulating material.' I

.;In the construction shown in Figs. 8and 9, the tube20 is provided with the outer metallic sleeve 35 spaced from-the tube and forming a plurality of air'chambers 38 which act as insulators; In.

the construction shown in these figures, themetal sleeve 35-is made up ofshort sections having steppedjoints 39 attheir ends, each section being provided with an integral circumferential flange 40 which,contacts intimately with the surface of theztube- With this arrangement,,heat absorbed by the covering is transmitted to the tube through the flanges by conduction and through the spaces between the flangeseby radiation, this radiatedheat increasing to a maximum when the covering becomes incandescent. Y

:In Fig. 10 there is illustrated a modified form of constructionsimilar to that shown in Figs. 8, and- 9. Here, the sleeve 35 is provided with longitudinal fins 41 whichincrease the-heat-absorbing surface of the sleeve. s

1.. In Figs. l1 and '12, there is illustrated a modification of the construction shown in Figs. 8 and In the-modified. arrangement, the tube;20 is enclosed withinasleeve 42 which, if desired, may be made up of short lengths. 43 with stepped joints (i4,-the sections being provided with longitudinal intrnalflflanges45 instead-of the circumferential iiangesaiO shown in Figs. 8 and 9. Between the longitudinal-flanges on the sleeve are 'air chamhere ,46 which serve as insulators.

the construction where air serves as an -insulation between the tube and covering I may substitute where necessary an. insulating or re-- fractorymaterial. :Constructions in which solid material replaces air as an insulator are shown in Figures 15 to 19, inclusive. 7 r In Figs. Band 14, there is disclosed still another modificationin which the outer surface of thecovered tube is composed inpart of refractoryand inpart' of metal. Mounted on the tube 20in intimate contact therewith is a sleeve/47 which is provided with a plurality of undercut openings 48 in which refractory material is car-.-

:rie'd The number, shape, size and arrangement 7 of these perforations in the sleeve may be varied in accordance with the purpose to which the'tube 1t will .be observed that in all of the construc-.

tions illustrated, the tube covering is in intimate contact with the surface of the tube and the tube is thus covered around its total circumference with a covering which may be varied as to material, thickness, and arrangement so as to control the rate of heat transfer to the contents of the tube. With these tubes, it is possible to maintain a hot or incandescent surface which promotes combustion, while the circulation of the contents of the tube limit the temperature to which the covering is raised during service. The refractory or insulating material or the air spaces in the covering are of lower heat conductivity than the metal part of the tube covering and the metal sleeves serve to hold the refractory or insulating material or to define air spaces around the circumference of the tube, as well as providing a path for the travel of heat to the exterior surface of the tube. In addition they serve to strengthen and protect the tube.

In the furnace practice, these tubes may be employed in the furnace chamber and in the region where combustion is taking place for the purpose of producing turbulence in andbreaking up stratification of the gases, with resultant improved and more rapid combustion. In oil still practice in which bare tubes are exposed to the furnace heat in the still, such tubes are subject to overheating and bursting due to carbonization of the oil on the interior of the tubes in local areas, which causes overheating of the tube. With the present covered tube, the rate of heat transfer to the tube contents is controlled, the heat more uniformly distributed around the tube and the tube strengthened against bursting so that the still can be operated at higher temperatures and with greater efficiency.

In the drawings, I have shown varying arrangements of the metal sleeve and of the refractory or insulating material. It is to be understood that the arrangement and thickness of the sleeve and the kind, arrangement, and thickness of the refractory or insulating mate- .rial may be varied as desired, and it may be applied in molded or plastic form.

I claim:

1. A tube structure which comprises a tube, a metallic covering over the tube and spaced therefrom throughout the greater portion of its extent, said covering having a multiplicity of extensions from its inner surface and disposed along its length, said extensions contacting with the outer surface of said tube and non-metallic material between the covering and the tube and in intimate contact therewith.

2. A tube structure, which comprises a tube, a metallic covering over the tube and spaced therefrom throughout the greater portion of its extent, said covering having a plurality of. extensions from its inner surface toward the outer surface of said tube and being made up of a plurality of cylindrical sections disposed from end to end along the tube, and non-metallic material between the covering and the tube and in intimate contact therewith.

3. A tube structure, which comprises a tube, a metallic covering over the tube and spaced therefrom, said covering having a plurality of extensions from its inner surface toward the outer surface of said tube and being made up of a plurality of cylindrical sections disposed along the tube from end to end and having expansion joints between the ends of adjacent sections, and insulating material between the covering and tube and in intimate contact therewith.

4. A tube structure which comprises a tube, a metallic covering over the tube having a multiplicity of extensions from its inner surface toward the outer surface of the tube, said extensions being disposed alongthe inner surface of said covering from end to end of the latter and insulating material between the tube and cov-' ering and in intimate contact therewith.

5. A tube structure,- which comprises a tube, I

a metallic covering over the tube and spaced therefrom, said covering having a multiplicity of extensions from its inner surface and spaced along the length thereof, said extensions contacting with the outer surface of the tube, and insulating material between the tube and covering and in intimate contact therewith.

6. A tube structure, which comprises a-tube, a metallic covering over the tube having a multiplicity of spaced portions along its length in direct contact with the tube, and insulating material held in position by said covering, said material having portions contact with said tube and with said covering. 1 7. A tube structure which comprises a tube, a metallic sleeve enclosing the tube and having a multiplicity of spaced portions along its length in intimate contact therewith, and masses of refractory material held in place by said covering, said masses being in intimate contact} with said tube and with said. covering. 8. A tube structure, which comprises a tub a metallic covering for the tube," and non-metallie material between the tube and covering and r in intimate contact therewith, said non-metallic material beingin the form of arcuate portions with material between adjacent portions permitting expansion thereof. l

9. A tube structure, which comprises a tube, a metallic covering therefor, and refractory material held in place by said metallic covering, said refractory material being made up of a plurality of arcuate blocks with material between the ends and sides of adjacent blocks permitting expansion thereof. 7

10. A tube structure, which comprises a tube,

a metal covering for the tube, and refractory, material held in place by said covering, said material being in the form of arcuate blocks with material between said blocks permitting expansion thereof.

11. A tube structure, which comprises a tube and a smooth bare metallic covering therefor having portions spaced from the tube and providing chambers between the covering and tube,

said covering having projecting flanges in its, inner surface extending circumferentially of the 

